In semiconductor manufacturing, ion implantation is used to change the material properties of portions of a substrate. Indeed, ion implantation has become a standard technique for altering properties of semiconductor wafers during the production of various semiconductor-based products. Ion implantation may be used to introduce conductivity-altering impurities, to modify crystal surfaces (pre-amorphization), to created buried layers (halo implants), to create gettering sites for contaminants, and to create diffusion barriers (F and C implant). Also, implantation may be used in semiconductors for non-transistor applications such as for alloying metal contact areas, in flat panel display manufacturing and in other surface treatment. All of these ion implantation applications may be classified generally as forming a region of material property modification.
One reason for the popularity of ion implantation is its versatility in types of applications as well as its ability to inject ion impurities to a precise depth—a feature particularly important as the level of integration of semiconductor devices increases.
Conventional ion implantation systems include an ion source that ionizes a desired dopant element which is then accelerated to form an ion beam of prescribed energy. This beam is directed to the surface of a workpiece. Generally, energetic ions of the ion beam penetrate into the bulk of the workpiece and are embedded into a crystalline lattice of the workpiece to form a region of desired conductivity. This ion implantation process is generally performed in a high vacuum, gas-tight process chamber which encases a wafer handling assembly and the ion source.
A typical ion beam path in prior art implantation systems includes an ion source, one or more electrodes, an analyzing magnet arrangement, an optical resolving element, and a wafer processing system. The electrodes extract and accelerate ions generated in the ion source to produce a beam directed toward the analyzing magnet arrangement. The analyzing magnet arrangement sorts ions in the ion beam according to their charge-to-mass ratio, and the wafer processing system adjusts the position of a workpiece relative to the ion beam path.
Ion implantation systems generally provide high voltages to produce acceleration energies necessary to implant ions into a substrate. Acceleration energies may range from 10-200 keV in many implantation systems to energies as high as several MeV in high-energy systems. Generally, such high voltages are applied via electrodes supplied by high voltage power supplies. Size becomes a constraint in designing such high voltage power supplies because of the possibility of overheating, flashover, and unintended voltage arcing. Furthermore, these high voltages can cause power supplies to fail over time at a faster rate than if operated at lower voltage levels. Thus, as you shrink the size of the device the system becomes more susceptible to arc break down and also to becoming flammable in the case of a break down.
Accordingly, it would therefore be desirable to have a system and method which mitigates such power supply overload and/or voltage collapse conditions.